Generations of students have been taught that birds descended from dinosaurs and that a particular bird, Archeopteryx, is not only an intermediate species between the two taxa but proof of their evolutionary relationship. Well, now it appears that all those students will have to unlearn that "fact" of evolutionary history. It turns out that there's conclusive evidence that birds did not arise from dinosaurs and that the common ancestor, if there is one, between the two groups is unknown.
This story from Science Daily recounts the bad news for those who for decades have cited Archeopteryx to refute those benighted creationist claims that there are no transitional fossils between dinosaurs and birds:
Researchers at Oregon State University have made a fundamental new discovery about how birds breathe and have a lung capacity that allows for flight - and the finding means it's unlikely that birds descended from any known theropod dinosaurs.
The conclusions add to other evolving evidence that may finally force many paleontologists to reconsider their long-held belief that modern birds are the direct descendants of ancient, meat-eating dinosaurs, OSU researchers say. It's been known for decades that the femur, or thigh bone in birds is largely fixed and makes birds into "knee runners," unlike virtually all other land animals, the OSU experts say. What was just discovered, however, is that it's this fixed position of bird bones and musculature that keeps their air-sac lung from collapsing when the bird inhales.
However, every other animal that has walked on land, the scientists said, has a moveable thigh bone that is involved in their motion - including humans, elephants, dogs, lizards and - in the ancient past - dinosaurs.
The implication, the researchers said, is that birds almost certainly did not descend from theropod dinosaurs, such as tyrannosaurus or allosaurus. The findings add to a growing body of evidence in the past two decades that challenge some of the most widely-held beliefs about animal evolution.
"For one thing, birds are found earlier in the fossil record than the dinosaurs they are supposed to have descended from," Ruben said. "That's a pretty serious problem, and there are other inconsistencies with the bird-from-dinosaur theories.
"But one of the primary reasons many scientists kept pointing to birds as having descended from dinosaurs was similarities in their lungs," Ruben said. "However, theropod dinosaurs had a moving femur and therefore could not have had a lung that worked like that in birds. Their abdominal air sac, if they had one, would have collapsed. That undercuts a critical piece of supporting evidence for the dinosaur-bird link.
The newest findings, the researchers said, are more consistent with birds having evolved separately from dinosaurs and developing their own unique characteristics, including feathers, wings and a unique lung and locomotion system.
There's more at the link. It's a fascinating thing about the whole evolution/creation debate that it seems like so many of the major discoveries in biology in the past two decades support what creationists have been saying since the 1950s. It must be terribly frustrating for the Darwinians, convinced as they are that creationists are a bunch of scientific simpletons, to see their favorite icons tumbled seriatim from their pedestals into the dustbin of history.
RLC